Biomass feed stock is useful in numerous industries such as the production of cellulosic ethanol, electricity production, heating fuels, and other commercial applications.
The 2005 Billion Ton study by the U.S. Department of Energy and U.S. Department of Agriculture concluded that agricultural and forest based biomass can displace 30% of the U.S. petroleum consumption by using approximately one billion dry tons of biomass feed stock per year.
The Energy Independence and Security Act of 2007 requires the United States to make one billion gallons of cellulosic ethanol from wheat straw, corn stover, rice straw, soybean stubble, milo stubble, forage sorghum, prairie hay, woodchips, cotton-gin residue, and a dozen other forms of agricultural waste. In the past, such waste materials have been generally considered to be of little or no value. In the past, meaningful volumes of cellulosic biomass agriculture material have not been brought to market on a commercial scale due to difficulties in integrating the supply chain to source, harvest, transport, storage, and processing of the material at a profit. Cellulosic ethanol producers and other renewable biomass users like electric utilities and industrial co-generation facilities require reliable, price-stable supplies of high quality biomass feed stocks. Successful and economic production of biofuels will facilitate independence from oil and petroleum-based fuels and reduce environmental concerns relating to production, transportation, storage, and use of such fuels; cellulosic biomass is the only real sustainable transportation liquid fuel. Thus, when correctly pursued, cellulosic ethanol can address many of the issues undermining national security and environmental well-being.
Biomass production from corn, soy, wheat, and other stover has not been practical or economical due to several barriers and risks. The use of crop stover in commercial scale production has been unsuccessful primarily due to (1) cost and logistics of stover (due to the low density of product) delivery for processing; (2) cost of protecting stored stover bales from weather and fire; (3) stover degradation; (4) stover pellet durability in withstanding standard handling and transportation; (5) inability to use current handling/storage infrastructure, resulting in high capital and operating costs; and (6) lack of a proven and reliable pellet processing of agriculture waste that works on a mass scale and does not use binding agents or other additives.
The stover agriculture residue and energy feed stock supply chain is an important component of large scale biofuel production and meaningful electric generation and has yet to be established, thereby slowing deployment of cellulosic, electrical generation, and other renewable energy technologies. The financial risks associated with feed stock ability to effectively be transported to market and processed on a continuous basis 365 days a year are a significant concern for investors and lenders.
Pelletizing of certain types of agricultural materials is an established practice. These agricultural materials are usually used as animal feed but more recently, some food crops such as hybrid corn, soybean oil, and sugar cane have been used for energy production Alfalfa is one example e of a feed crop that has been pelletized for years. Although is has only been used on a very small scale for fuel pellets, Alfalfa has come under fire in the food for fuel debate. These types of feed crops contain protein, sugar, and/or fat which serve as a natural binder in the pelletizing process.
Pelletizing non-food and non-primary feed crop residues have been problematic due to the lack of natural binders. For example, corn stover, soybean stubble, wheat straw, fruit tree trimmings, and walnut shells do not contain substantial protein to act as a natural binder. Thus, binder additives have to be used to facilitate pellet formation, which adds costs and creates emission concerns when burned such that use in electricity generation is undesirable or unfeasible due to environmental issues. Also, pellets made with binders are subject to decomposition and breakdown during normal handling, storage, and transport, which decreases the percentage of useful pellets. Also, crop residues have been used as a feed additive due to the fiber content, but is not a primary feed for livestock.
Furthermore, tapered dies used for pelletizing alfalfa and similar crops do not work for pelletizing stover, stubble, and stalks due to the stringy quality of these residues, which tend to plug the tapered dies. Also, shredded and ground alfalfa has a density of approximately 12 pcf, which conveys easily with pneumatic conveyors. However, shredded and ground crop residue is much lighter, for example +/−6 pcf, which is not conducive to pneumatic conveying and creates issues in pelletizing the stover material.